Well, I wish I could offer something better than this, but maybe some others may be able to offer something more elegant. Eveything I tried didn't work. Suggest at least to attempt the following.
Download both the Linux and DOS smart boot manger from http://btmgr.sourceforge.net
and store on a floppy disk.
Boot 8.0 CD to provide a base OS to work from.
Install Smart boot manager to the mbr of the hard disk.
If you are unable to mount the USB floppy under Slack 8.0 then I suggest try using a DOS disk to boot, even just a Win98 CD or something. You may need to create small DOS partition to work from. But it can be deleted later. Again install SBM to the mbr of the hard disk.
Then reboot. You may even want to remove the USB floppy drive in case that was giving a problem when booting SBM from a floppy disk.
If smart boot manager boots and offers to boot the CD then do it and proceed with install. Sometimes SBM will report the drive not ready on the first or second attempt. But it almost always works by the third attempt. I think it has to do with the delay of the CD drive coming ready.
If this works then I suggest leaving smart boot manager on the hard disk. Creating partition 1 as bootable and install lilo there on hda1. I had an old notebook that I installed it on, because the BIOS did not support booting any CD's. The boot manager can be set to default to any device in the list after say five seconds and allows booting any readable partiton if you want a mutliboot config. Then set lilo to no delay. This would allow you the option to boot the CD if you need to recover from something in the future.
Hope it helps. As a last resort you might want to see how difficult it is to remove the hard disk. Install the hd in another system to setup the base system and insure that it boots, then reinstall in the notebook. This requires a 3.5" to 2.5" IDE adapter.
I'll post back if I can think of anything else.